Mayer Brown Deepens Tokyo Buildout with Fresh AO Shearman Partner Hires

Mayer Brown has continued its hiring push in Tokyo with the addition of partners Toshiro Mochizuki and Kana Morimura from A&O Shearman, further building out a team around recently appointed Tokyo managing partner Masahisa Ikeda and underscoring a more deliberate rebuild of its Asia platform.

With the addition of Mochizuki and Morimura, Mayer Brown has added six partners in Japan this year. Their arrival marks the latest step in Mayer Brown’s efforts to reconstruct its Japan offering around U.S. law capability and cross-border advisory work.

The addition expands the firm’s Tokyo bench, deepening its ability to support Japanese companies across the full corporate life cycle, from capital raising and cross-border transactions to regulatory compliance, investigations and complex disputes.

The hires add depth across both transactional and contentious practices.

Mochizuki advises issuers and underwriters on global offerings, U.S. Securities and Exchange Commission registrations and reporting, and corporate governance matters, as well as cross-border transactions and compliance issues, including sanctions and merger clearance.

Morimura focuses on disputes and investigations, advising on multi-jurisdictional regulatory probes, anti-bribery and antitrust matters, fraud and False Claims Act cases, as well as commercial disputes and product-related issues. She also counsels on internal investigations, class actions and compliance program design for Japanese companies operating globally.

Ikeda, Mochizuki and Morimura previously worked together at A&O Shearman and were part of the legacy Shearman & Sterling practice that combined with Allen & Overy to form the merged firm. Ikeda left A&O Shearman last year.

Mochizuki has spent more than 13 years at A&O Shearman, joining the legacy U.S. firm in 2012 and making partner in 2018. Prior to that, he worked for six years as in-house counsel at an international investment bank.

Morimura has spent 15 years at A&O Shearman, joining legacy Shearman & Sterling as an associate in 2011 and making partner in 2021.

Ikeda said the pair’s combined experience strengthens the firm’s ability to guide clients through increasingly complex cross-border matters.

“Toshiro and Kana each bring a caliber of experience that is highly relevant to the challenges Japanese companies face today,” he said in a statement. “Their understanding of U.S. regulatory expectations and cross-border transactional dynamics strengthens our ability to deliver clear, practical guidance on matters that span multiple markets.”

The hires build on Mayer Brown’s earlier recruitment of Ikeda, as well as its recent additions in energy and infrastructure finance. Project finance lawyers Andrew Pendleton and Justen Fleming joined in Tokyo from Milbank, alongside former Milbank lawyer Andrew Gibb in Singapore and Fiona Gulliford from Trinity.

Taken together, the moves form part of a broader strategy to rebuild selectively in Asia after several years of contraction.

In January, three contentious partners left Mayer Brown’s Singapore joint law venture to establish an independent practice. In 2024, the firm ended its longstanding association with Hong Kong partner Johnson Stokes & Master, exiting mainland China and significantly reducing its bench in Hong Kong. The split also led to the closure of its offices in Beijing, Shanghai and Vietnam, leaving the firm with a diminished regional footprint.

Since then, the firm has shifted its focus toward Tokyo, which has emerged as a central pillar of its Asia strategy, particularly as Japanese corporates continue to expand overseas and require U.S. law advice on capital markets transactions, M&A and compliance.

The recent hires have begun to reshape Mayer Brown’s Tokyo office, which has grown and now combines U.S. securities, M&A, investigations and project finance capabilities. The new additions will give Mayer Brown a total of nine partners in Japan.

At A&O Shearman, the departure of Mochizuki and Morimura leaves the firm with seven partners remaining in Tokyo, none of whom focus on capital markets or disputes. Two of the remaining Japan-based partners are from the legacy Shearman & Sterling practice.

“We thank both Toshiro and Kana for the contribution they have made to the firm and wish them all the best for the future," an A&O Shearman spokesperson said.

Reprinted with permission from the March 26th edition of Law.com © 2026 ALM Properties, Inc. All rights reserved. Further duplication without permission is prohibited.